1. Field of the Invention
The present invention relates to a magnetic recording device such as a hard disc device.
2. Description of the Prior Art
A magnetic recording device typically includes a recording medium such as a magnetic disc, a spindle motor for rotationally driving this recording medium, an electromagnetic means such as a magnetic head for writing and/or reading magnetic information to and/or from the recording medium and a shift means for shifting the electromagnetic means along the surface of the recording medium. The spindle motor has a housing mounted on, e.g., a frame of the magnetic recording device, a hub relatively rotatable about the housing, a rotor magnet attached to the hub and a stator disposed opposite to this rotor magnet. The recording medium is fitted to the hub as required.
In this type of magnetic recording device, an electric current supplied to a coil of the stator is, as required, commuted corresponding to an angular position of the rotor magnet. The recording medium is thereby rotationally driven together with the hub in a predetermined direction. The electromagnetic means is, as required, shifted by action of the shift means, whereby the magnetic information is written and/or read to and/or from the recording medium.
However, electromagnetic noises tend to occur due to the commutation of the current to the coil. When the electromagnetic noises are caused, those noises exert adverse influences on the electromagnetic means via the frame of the recording device. This in turn causes errors during a write and/or read process. Particularly when writing and/or reading is effected based on digital signals, and if the electromagnetic noises are pulse-like ones, it is difficult to eliminate those noises. This also causes the errors during the write and/or read process.
Besides, in the magnetic recording device, a magnetic flux generated leaks outside from the stator and exerts adverse influences on the electromagnetic means. This causes the errors during the writing and/or reading process.